Process and apparatus for forming and annealing sheet glass



F. GELSTHARP PROCESS AND APPARATUS FOR FORMING AND ANNEALING SHEET GLASS Filed Jar 23, '1922 0y VEN TOR vided with Patented Oct. 28, 1924.

FREDERICK GELSTHARP, OF TARENTUM, PENNSYLVANIA, ASSIGNOR TO PITTSBURGH' PLATE GLASS COMPANY, A. C0

RPORA'I'IO'N OF PENNSYLVANIA.

PROCESS AND APPARATUS FOR FORMING AND AN NEALI NG SHEET GLASS.

Application filed January 28, 1922. Serial No. 531,055.

To all whom it may concern:

Be it known that I, FREDERICK GELS- THARP, a citizen of Great Britain, and a resident of Tarentum, in the county of Allegheny and State of Pennsylvania, have made a new and useful invention in Improvements in Processes and Apparatus for Formin and Annealing Sheet'Glass, of which the following is a specification. m

The invention relates to an apparatus and process for which is produced in ribbon form. This ma be accomplished in connection with a rib on forming operation carried on by continuous delivery from a tank as shown and described in' my application Serial No. 493,311, filed August 18th, 1921, or by some other tank delivery apparatus capable of producing a plastic ribbon, or by. a pouring operation as shown and described in the present application. One form of apparatus for carrying out the process is illustrated in the accompanying drawing, wherein:

The figure is a vertical section through the apparatus shown in very simple diagrammatic form.

As here shown, rolls carrying upon their axles the intermeshing spur gears '3 and 4, the gear 4 bemg driven from a pinion 5 itself driven by sultable power means not s own. The rolls 1 and 2 are preferably made hollow and prosuitable cooling means such as shown in said application may be circulated through connections a whereby water the rolls to plate 6 and end lates 7 "serve to provide a hopper construction for holding the body of molten glass which is. to be rolled into a continuous ribbon. The glass may be supplied to the rolls by means of a pot carried by a crane as' is done in the ordinary plate glass casting operation.

Placed in front of the rolls and in line therewith is an annealing leer 8', provided with a series of rollers 9 for advancin the ribbon formed between the rolls thou the leer. These rolls are driven and placed sufliciently close together to revent the glass sagging at the entrance en of the leer. The

glass enters at this point in a semi-plastic or yielding condition, and if the rollers were set too far apart there would be a tendency.

of the glass .to bend intermediate the rollers.

By placing the rolls closetogether and drivproducing annealed sheet glass,-

1 and 2 are a pair of feed prevent overheating. A back' ing them, the glass-iskept perfectly flat, this requirement articularly existing at the entrance end of the leer, as in later stages the glass is suificiently' stifi' to maintain itself against bending even though the rolls are spaced a considerable distance apart. The leer is divided into two partsby the bafiie walls 10 and 11, the portion nearest the rolls being the annealing end, while the other portion is the cooling end. The baflie walls 10 and 11 come very close to the glass so that there is no circulation of air from the cooling end to the annealing end, and if desired these walls may be provided at their ends with yielding portions of, asbestos 10 or other suitable material for actually contacting with the glass. The annealing end may be heated in any suitable manner, as, for instance, by the burners 12, althou h a very considerable amount of heat is derived from the ribbon itself, which enters the leer when it is'of a red color and upwards of 1200 .F. The length of the annealing end is made such that in'passing through,this portion the ribbon drops through 'a range from the setting point, which is. about 1200 F., tea temperature of about 950 F. Thls drop 1n temperature must be made slowl in order to secure the proper annealing e ect and remove any strain which exists in the glass. This annealing action all occurs above the 950 F. point whichis comriidfily referred to as the critical annealing range, so after the glass drops below this point it is not adversely efiected by a very rapid cooling.

From the bafile walls on through the cooling end of the leer it is desirable to secure a rapid drop in temperature in order to keep the leer at a minimum length and save time. Various means may be applied for hastening the cooling of the glass during its travel through this ortion of the leer but the means referaiily employed is a circulation of air ongitudinally of the glass, which is accomplished by providing the stack12 and by the use of afan-13 or.. other suitable means drawin the air through this stack and through t e length "of thecooling end of the leer. Various other expedients may, of course, be employed .for giving the desired circulation. The glass is preferably cooled so that it leaves the leer at a temperature around 200, at which temperature it can be readily handled. Since the of the glass sheet is chilled by contact with the rolls 1 and 2 while the interior of the sheet is at a much higher temperature, it is necessary, in order to avoid warping and strain due to this uneven heat condition, to bring the sheetito uniform temperature after the sheet passes such rolls and either before or immediately after it enters the leer. In my copending application, Serial Number 656,441, burners are shown for applying the necessary heat before the glass enters the leer, but no such means are shown here, as the application of this additional. heat'may be accomplished in the entrance portion of the leer. This secures a uniform temperature of the sheet.

so that it will flatten out as it passes along the rolls, if not already perfectly fiat, and will keep such flatness during the entire annealing operation.

The operation produces very flat glass having a surface which is much smoother than that of ordinary cast plate glass, so that the glass may be made thinner and the cost of grinding is materially reduced. The leer, by reason of the complete separation of the annealing and cooling ends, can be made much shorter than the ordinary plate glass leer, so that the operation of annealing is more rapid and less expensive and the cost of the leer is also much less because of its size and because of the simplicity of its construction. The upkeep of a leer of this kind is also much less than the ordinary plate glass leer. The foregoing and other advantages will be readily appreciated by those skilled in the art.

What ll claim is: y

1. A process of forming sheet glass which consists in rolling a molten mass of glass into a ribbon, feeding the ribbon while at a high temperature into a leer, maintaining the glass flat in the leer while'advancing it therethrough, causing the glass to cool slowly from the temperature of setting-to a temperature of approximately 950F, and then applying artificial cooling means to the ribhon to hasten its cooling during the remainder of its progress through the leer.

2. A process of forming sheet glass which consists in rollin a molten mass of glass into a ribbon. fee ing the ribbon into a leer, maintaining the glass flat while advancing it through the leer, causing the glass to cool very slowly as it passes through the first part of the leer and while it is cooling from into an annealing end and a cooling setting temperature to approximately 950]F, and then applyin means to cause a more rapid cooling of t e ribbon during its last period of travel through the leer.

3. A process of forming sheet glass which consists in rolling a molten mass of glass into a ribbon, feeding the ribbon into a leer 1 while still plastic, maintaining the glass while advancing it through the leer and causing it to cool very slowly until it reaches a temperature below the critical annealing range, and then applying means to cause the rapid cooling of the glass during its last rio-d of travel through the leer.

In combination with means for form ing and feeding ahead a ribbon of pl tic glass, of a leer in line therewith proviu L with rollers for advancing the ribbon t through, means dividin" the leer into annealin end and a one ing se ing off t e annealing end against cur? of air from the cooling end, and means circulating a cooling current of air longitudinally of the said coolingiend from the outer end thereof inward to promote the rapid cooling of the ribbon after it leaves saidannealing end.

5. In combination with means for forming and feeding ahead a ribbon of plastic glass, of a. leer in line therewith provided with rollers for advancing the ribbon there through, baffle means extending from the upper side of the glass to the ceiling of the leer and from the lower side of the lass to the floor of the leer for dividing le QED and means to cause the rapid cooling or ribbon during its last period of travel. throu h the leer.-

6. process of forming sheet glass which so consists in rolling a molten mass of glass into a ribbon of uniform thickness between cooled rolls which provides a sheet of glass cooler at the surface than in its center, bringing the sheet to uniform temperature from to?) surface to surface at a temperature above the setting point of the glass, allowing the glass to cool very slowly through the critical annealing range, and then applying means to cause a rapidcooling of the glass.

In testimony whereof, l have hereunto subscribed my name this 16th day of January, 1922.

rnnnnnicir GELSTHARP.

- ice 

